DRV2667: Does the VBST of 2 device can merge into a single supply

Xiang Maverick

Part Number: DRV2667

The idea from the thread (DRV8662: Drives two cascaded piezo ceramic - Motor drivers forum - Motor drivers - TI E2E support forums) should be made a modification because the piezo is connected in a product in a way described in the following figure.

The following figure is the final design in the previous thread. Apparently, we should use two devices. Each device will output a 105V supply? How can they merged into a single supply?

over 1 year ago

0 Arthur Brown over 1 year ago

TI__Genius 16950 points

Hi Xiang,

If I understand correctly you are saying that the piezo device is 2 Piezo in series, and then two sets are connected in parallel?

If you where to use two devices it should not risk device damage to short the PVDD voltages of each device together is they are both set to 105V

Regards

Arthur

0 Xiang Maverick over 1 year ago in reply to Arthur Brown

Intellectual 750 points

“If I understand correctly you are saying that the piezo device is 2 Piezo in series, and then two sets are connected in parallel?”

Yes.

There should be slight difference even if the ideal value is 105V. Why the difference would not create damage?

0 Arthur Brown over 1 year ago in reply to Xiang Maverick

TI__Genius 16950 points

Hi Xiang,

The voltage difference shouldn't result in damage as the voltage will still be within the rated voltage for the PVDD. however it may be wise to use a diode between the PVDD of each device and the 105V connection of the actuator. this would ensure that the DRV2667 devices are not 'fighting' eachother

Regards,

Arthur

0 Xiang Maverick over 1 year ago in reply to Arthur Brown

Intellectual 750 points

Thank you

Would you please possibly give a figure describing the connection?

Do I need to use a resistor to connect PVDD of the 2 devices?

0 Xiang Maverick over 1 year ago in reply to Arthur Brown

Intellectual 750 points

Hi @Arthur Brown

Thank you

Would you please possibly give a figure describing the connection? I am not sure I get a correct understanding on your description of the wise connection. "The voltage difference shouldn't result in damage as the voltage will still be within the rated voltage for the PVDD. however it may be wise to use a diode between the PVDD of each device and the 105V connection of the actuator. this would ensure that the DRV2667 devices are not 'fighting' eachother"

+1 Arthur Brown over 1 year ago in reply to Xiang Maverick

TI__Genius 16950 points

Hi Xiang,

Sorry for the delay here I have had very limited bandwidth the past few weeks.

This is a diagram of my suggestion

Using appropriately rated diodes (that can handle reverse voltages of 105V) this configuration would ensure that the any slight differences in the voltages between devices would not interfere with one another

Regards,

Arthur

+1 Xiang Maverick over 1 year ago in reply to Arthur Brown

Intellectual 750 points

@Arthur Brown

From what we disscussed at previous thread (DRV8662: Drives two cascaded piezo ceramic - Motor drivers forum - Motor drivers - TI E2E support forums), if the voltage control1 rises, the upperside piezo will discarge and the lowerside piezo will charge, the current discharged from the upperside piezo may flow through VBST to the lowerside piezo. For this reason I make a modification. Do you think it seems more reasonable?

Thank you.

+1 Arthur Brown over 1 year ago in reply to Xiang Maverick

TI__Genius 16950 points

Hi Xiang,

I think that you are correct. the configuration you shared would ensure that the PVDD voltages for each device are the same even if the output of the boost converter is not the same between devices. and this configuration also maintains the current path from the upper side piezo to lower side piezo.

I think that your suggestion is better.

Regards,

Arthur